Tracer gas technique for measurement of air infiltration and natural ventilation: case studies and new devices for measurement of mechanical air ventilation in ducts

摘要

In buildings without mechanical ventilation, the fresh air needed by the occupants is supplied only by air infiltration or natural ventilation. Its quantification by analytical methods is difficult, and so experimental methods such as the tracer gas technique are very useful. In this work, several case studies are presented, where one may see the potential of this technique to detect small differences in building air tightness, due to different envelope elements, namely the type of window frames and location of blinds' boxes. The applicability of this technique to other spaces rather than buildings can also be analyzed. When dealing with mechanical ventilation, it is difficult to measure the duct air flow rate precisely, because of the minimum duct length necessary to obtain a good mixing of the tracer gas with the air, when conventional probes are used. Research was carried out with the development of new probes to overcome this situation, and results are also shown. With accurate measurements of air flow rates, it is possible to reduce CO_2 emissions due to air heating or cooling in buildings.